164 MARINE SAUE.IANS. 



Comparing these extremities with those of other verte- 

 brated animals, we trace are gular series of links and gra- 

 dations, from the corresponding parts of the highest mam- 

 malia, to their least perfect form in the fins of fishes. In 

 the fore paddle of the Plesiosaurus, we have all the essential 

 parts of the fore-leg of a quadruped, and even of a human 

 arm ; first the scapula, next the humerus, then the radius and 

 ulna, succeeded by the bones of the carpus and metacarpus, 

 and these followed by five fingers, each composed of a con- 

 tinuous series of phalanges. (See PI. 16, 17, 19.) The 

 hind paddle also offers precisely the same analogies to the 

 leg and foot of the Mammalia; the pelvis and femur are 

 succeeded by a tibia and fibula, which articulate with the 

 bones of the tarsus and metatarsus, followed by the nume- 

 rous phalanges of five long toes. 



From the consideration of all its characters, Mr. Cony- 

 beare has drawn the following inferences with respect to 

 the habits of the Plesiosaurus Dolichodeirus, " That it was 

 aquatic is evident, from the form of its paddles; that it was 

 marine is almost equally so, from the remains with which 

 it is universally associated ; that it may have occasionally 

 visited the shore, the resemblance of its extremities to those 

 of the Turtle may lead us to conjecture; its motion how- 

 ever must have been very awkward on land ; its long neck 

 must have impeded its progress through the water; pre- 

 senting a striking contrast to the organization which so ad- 

 mirably fits the Ichthyosaurus to cut through the waves. 



ber to accommodate them to the corresponding- office of a paddle. The mode 

 of connexion between the joints was (like that in the Whales,) by synchon- 

 drosis. The phalanges of the Plesiosaurus present a link, between the still 

 more numerous and angular joints of the paddle of the Ichthyosaurus, and 

 the phalanges of land quadrupeds, which are more or less cylindrical ; in- 

 these sea Lizards they were flattened, for the purpose of giving breadth to 

 the extremities as organs of swimming. As its paddles give no indication 

 of having carried even such imperfect claws, as those of the Turtles and 

 Seals, the Plesiosaurus apparently could have made little or no progress in. 

 any other clement than water. 



